At present, cutting or grinding processing is still main process means for the finally formation of components. One of the main development directions of cutting machining is high-speed cutting (including high-speed soft cutting, high-speed hard cutting, high-speed dray cutting and large feed cutting, etc.). Going through the four stages of theoretical exploration, application exploration, preliminary app3lication and mature application, high-speed cutting technology has achieved a certain development and promotion, and the cutting speed for processing the steel has reached 2000 m·min−1, and 3000 m·min−1 for processing cast iron, and 7000 m·min−1 for aluminum alloy, which is 5˜10 times of common cutting speed. High-speed cutting has drawing more and more attention in industry, because it has significant advantages relative to traditional processing, such as short processing time, (high efficiency and low cost), high-quality workpiece surface (high surface accuracy), cooling liquid free (green processing and no environmental pollution) and can process special materials such as quenched steel which is difficult to deal with for traditional processing.
To be used as high-speed cutting cutter material, the materials should have good mechanical property and thermal stability, specifically, it should have properties such as high hardness, shock resistance, wear resistant and thermal fatigue resistance. At present, high-speed cutting cutter materials used in industry are mainly cemented carbide, composite silicon nitride ceramics, cubic boron nitride and diamond, etc. Composite material formed by WC and cBN will have the advantages of the two materials. The introduction of super hard cBN will not only significantly improve the hardness and wear resistance of WC cemented carbide, but in condition that, it was used as superhard particles in the composite materials, which will trigger crack deflection so as to further improve the toughness of the material, and due to the combination of performances of good hardness, wear resistance and toughness, WC-cBN composite materials are used as the most potential new generation material in cutter filed, and has caused extensive intention in the worldwide. In 2007, Martinez etc. from National university of Navarre in Spain has prepared WC/Co-cBN composite materials with different cBN content by hot isostatic pressure method. When the cBN content is 30 vol %, the hardness of the composite material is 25 Gpa; when the content of cBN is improved to 50 vol %, more Co sintering aids will be required which will lead to the phase change from cBN to hexagonal boron nitride, and the hardness of the composite material is reduced by 4 GPa (Journal of the American Ceramic Society, 2007, 90, p 415-424). In 2009, Yaman etc. from Eskisehir Osmangazi university of Turkey has prepared WC/6 wt % Co-cBN composite materials with a cBN content of 25% using spark plasma sintering method, though the toughness has reached 12 MPam1/2, the highest hardness is only about 21 GPa (Materials Letters, 2009, 63, p 1041-1043), which is lower than the value reported by Martinez. In 2012, Rosinski etc. from Warsaw University of Technology in Poland has prepared WC/Co-cBN composite material using pulse plasma sintering method, the volume content of the prepared cubic boron nitride is 30%, and the highest hardness is about 23 GPa (Journal of Materials Science, 2012, 47, p 7064-7071). In 2007, Xiaoliang SHI etc. from national key laboratory of new technology of composite materials of Wuhan University performed pretreatment to cBN by coating metallic titanium (Ti) to the surface using chemical vapor deposition method, and prepared WC-10Co-cBN composite material with a cBN volume fraction of 30% using hot pressed sintering method under 30 MPa, 1380° C. for 60 min, the prepared material has a relative density of 94.2% and an intensity of 750 MPa (Material Of Mechanical Engineering, 2007, 31, p 71-73). Besides these scientific research institutions, Sandvik Intellectual Property Ab. (world's leading cutting tool manufacturers) from Sweden has also disclosed a patent on WC-cBN composite material (Method for producing a sintered composite body, Patent WO2012038529A2, Sandvik Intellectual Property Ab.), using Co as sintering aids, and prepared WC/Co-cBN composite material under 1350° C. using pressureless sintering, but the highest hardness of the prepared composite material is 13 GPa.
In conclusion, though preliminary achievement of the WC-cBN composite material has been gained home and abroad, there still exist problems such as difficult to densification, deficiency in hardness and wear-resisting property in composite material. WC and cBN are both material hard to be sintered, usually their composite materials can be prepared using Co, Ni etc as sintering aids (with a common weight content of about 6-15 wt % or higher) and performing pressureless sintering or pressure sintering under high temperature for a long time. But the hardness of metals such as Co, Ni is low, which will lead to the reduction of the hardness of the composite material, especially for red hardness. On the other hand, high content metal sintering aids will also accelerate the phase change from cBN to hexagonal boron nitride (hBN). Moreover, hBN is soft graphite phase, which has a similar hardness as graphite, so the phase change from cBN to hBN will also cause hardness reduction of the composite material. In addition, the volume change caused by the phase change will lead to the increment of material porosity, which will also cause the reduction of the hardness and wear-resisting property for the cutter materials, and led to the further shorten life time of the material.